The present invention relates to mixing capsules, particularly to such capsules in which materials to be mixed are normally kept separated and are brought together only at the time they are to be mixed. One application of such mixing capsules is in the preparation of dental silver amalgams, and the invention is therefore described below particularly with respect to such an application.
In preparing dental silver amalgam for use in filling teeth cavities, a silver alloy is mixed with liquid mercury in a high speed vibrator-mixer. Several different types of mixing capsules have been provided for this purpose. In one of the most popular types, the mercury is kept separated from the silver alloy by means of a plastic partition frictionally retained in a tubular extension of the housing which partition is forced into the mixing chamber by the plunger when depressed by the user. In this type of mixing capsule, however, there is a danger that the partition will drop into the mixing chamber when the capsule is being assembled, or during handling after the materials have been added, the latter causing a premature mixing of the materials. In addition, there is a danger that the mercury may seep around the edges of the partition and enter the mixing chamber prematurely, or that it may seep around the edges of the plunger out of the capsule, particularly during the high-speed mixing after the partition has been removed, the latter especially producing a serious health hazard in view of the highly toxic nature of mercury.
The present invention provides a mixing capsule having advantages in the above respects.